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SAFETY & SECURITY Last modified on June 2, 2017

What lies beneath

Is it time for the introduction of new technology to check the underside of vehicles at security checkpoints at airports? Colin Williams considers the options.

Airports should check the underside of vehicles at security checkpoints to restricted areas as part of a layered approach to security across the airport site.

However, there is pressure for high-volume traffic areas to maintain efficient flow, which must be effectively balanced against security needs.

For many years, the most commonly used system has been a convex mirror mounted on a stick. However, typically only the edges of the vehicle’s underside can be seen with any clarity. Also, while this method is relatively safe for the operator when drugs or other illegal goods are detected, the proximity to the vehicle causes obvious safety concerns if a potential bomb threat exists. 

Another method, which offers complete viewing of the underside of the vehicle, is to install an inspection bay at the checkpoint, which must be sunk into the ground. But as the operator needs to physically view the underside of the vehicle, this also creates safety and delay issues. This results in insufficient time to properly review vehicles, or the introduction of checking quotas. 

The first computer-based Under Vehicle Surveillance System (UVSS) was developed in the late 1980s and provided low-resolution, black and white images. Since then, this has developed into a more effective system, with three alternative camera technology options available. 

The least sophisticated option uses video cameras to present a moving image to the operator. Another employs area scan cameras, which stitch images together in the same way that a panoramic photograph is produced. 

The third option is line-scanning cameras, which work like a photocopier – rapidly scanning from one side of the vehicle’s underside to the other – to deliver a continuous image, full colour, high-resolution image to help any anomalies easily stand-out. 

The major benefit of using such computer-based UVSS is that every vehicle can be checked and a complete view of the underside of the vehicle is presented, giving the security team 100% coverage of every vehicle passing through the control gate. 


In 2014, Gatwick Airport made a major investment in its road-to-airside security gates, replacing the mirror on a stick approach to improve detection rates of prohibited articles and explosives, while allowing vehicles to access airside more effectively and efficiently. The four-lane vehicle screening facility monitors the high volume of airport traffic, including staff, maintenance and catering vehicles. 

By integrating the UVSS with an Automated Number Plate Recognition (ANPR) system, individual vehicles can also be linked to their under-chassis scans. This will prove invaluable to increase security effectiveness and support post-event reviews, as well as indicate vehicles that are blacklisted, such as contractors trying to gain access to the site when their pass has expired. 

Indeed, Gatwick’s system uses ANPR to cross check each vehicle against the airport database to ensure they are approved to access the airfield. ANPR also enables Gatwick to report on vehicle queue times, which can then be used to improve the efficiency of staffing rotas, as well as better understand who is on and off site.

Whichever UVSS is used, it is important that the operation is overt. Not only does this give a sense of safety assurance to visitors and staff at facilities, it also provides a visible deterrent to those who might consider smuggling contraband or concealing a bomb. 

However, effective operator training and experience is essential, as it is not the system which spots potential threats, but the person. Over time, operators will become increasingly adept at identifying a range of illicit items, ultimately providing a more robust way of improving security. 

As with all technology, it is only as good as the person using it, but these technological advances now mean that airport security can be significantly enhanced. 

About the author

Colin Williams works for Chemring Technology Solutions where he is product manager for its VehicleScan under vehicle surveillance system.

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